hippocampus

American  

[hip-uh-kam-puhs] / ˌhɪp əˈkæm pəs /

noun

• hippocampi
  plural

1. Classical Mythology. a fish-tailed horse of the sea that was ridden by the sea gods.

2. Anatomy. an enfolding of cerebral cortex into the lateral fissure of a cerebral hemisphere, having a major role in learning, emotion, and memory, and named for the seahorse shape of its cross section.

---

hippocampus British  

/ ˌhɪpəʊˈkæmpəs /

noun

1. a mythological sea creature with the forelegs of a horse and the tail of a fish

2. any marine teleost fish of the genus Hippocampus, having a horselike head See sea horse

3. an area of cerebral cortex that forms a ridge in the floor of the lateral ventricle of the brain, which in cross section has the shape of a sea horse. It functions as part of the limbic system

---

hippocampus Scientific  

/ hĭp′ə-kăm′pəs /

• hippocampi
  plural

1. A convoluted, seahorse-shaped structure in the cerebral cortex of the temporal lobe of the brain, composed of two gyri with white matter above gray matter. It forms part of the limbic system and is involved in the processing of emotions and memory.

---

Other Word Forms

Derived Forms

• hippocampal
  adjective

Inflected Forms

Nouns

• hippocampi
  plural

Etymology

Origin of hippocampus

First recorded in 1575–80; from Latin hippocampus, hippocampos, from Greek hippókampos, equivalent to hippo- hippo- + kámpos “sea monster”

Explanation

A hippocampus is a complex neural structure that's part of the brain. Your brain has two hippocampi, and they're important for memories and emotions. This word has a complex history. Originally, it meant a seahorse, and it has also meant a small fish that resembles a seahorse. That resemblance is why the brain structures known as the hippocampus major and hippocampus minor have that name: they look kind of like seahorses too. The hippocampi are found on the floor of your brain's ventricles, and they are vital to feeling and remembering. Without your hippocampi, you wouldn't be who you are.

Example Sentences

See Examples For:

hippocampus hippocampi

“Indelible in the hippocampus is the laughter,” Ford tells Sen. Patrick Leahy when asked about the strongest memory she has of the incident.

From Los Angeles Times ● Sep. 18, 2026

The changes were accompanied by higher D-serine levels in the hippocampus, a brain region essential for learning and memory.

From Science Daily ● Sep. 18, 2026

Early in the disease, regions around the hippocampus, deep within the brain's temporal lobes, are among the first to be affected.

From BBC ● Aug. 31, 2026

"Turning neurogenesis back on may be a way to treat depression in some people by rewiring their hippocampus circuit."

From Science Daily ● Aug. 25, 2026

Rainbow, the hippocampus, burst out of the waves.

From "The Sea of Monsters" by Rick Riordan

Four weeks later, these mice showed increased numbers of newly-formed neurons in their hippocampi, and importantly, the PTSD-like behaviors were less severe, compared to the double-shocked mice without wheel access.

From Science Daily ● May 20, 2024

After nearly 1 month, the number of new neurons in the rodents’ hippocampi had doubled.

From Science Magazine ● Feb. 3, 2022

The hippocampi, paired structures in the temporal lobe that are crucial in the formation of new memories, are studded with cannabinoid receptors.

From Scientific American ● May 7, 2020

In the 1970s, O'Keefe had discovered neurons called place cells in the hippocampi of rats.

From Nature ● Oct. 5, 2014

The hippocampi were swimming around frantically, wanting to help but not sure how.

From "The Titan's Curse" by Rick Riordan